Interactions during development of the retina, dorsal lateral geniculate nucleus and striate cortex of the monkey visual system will be studied from early fetal to adult ages. The establishment of characteristic cell types and synaptology will be studied for dorsal lateral geniculate neurons using Golgi impregnation, electron microscopy, and the autoradiographic and horseradish peroxidase methods for tracing neuronal connectivity. The normal development of function in the visual system will be followed after birth at the cellular level by neurophysiological recording and at the performance level by behavioral testing. Monocular pattern deprivation will be induced in newborn monkeys and its effect on the visual system compared with the normal using the same morphological, neurophysiological and behavioral techniques. Experiments are proposed to prevent the formation or to restore the function of an amblyopic eye.